Query : 2007A&A...475..549B

2007A&A...475..549B - Astronomy and Astrophysics, volume 475, 549-558 (2007/11-4)

Energetic radiation and the sulfur chemistry of protostellar envelopes: submillimeter interferometry of AFGL 2591.


Abstract (from CDS):

The chemistry in the inner few thousand AU of accreting envelopes around young stellar objects is predicted to vary greatly with far-UV and X-ray irradiation by the central star. We search for molecular tracers of high-energy irradiation by the protostar in the hot inner envelope.The Submillimeter Array (SMA) has observed the high-mass star forming region AFGL 2591 in lines of CS, SO, HCN, HCN(ν2=1), and HC15N with 0.6'' resolution at 350GHz probing radial scales of 600-3500AU for an assumed distance of 1kpc. The SMA observations are compared with the predictions of a chemical model fitted to previous single-dish observations.The CS and SO main peaks are extended in space at the FWHM level, as predicted in the model assuming protostellar X-rays. However, the main peak sizes are found smaller than modeled by nearly a factor of 2. On the other hand, the lines of CS, HCN, and HC15N, but not SO and HCN(ν2=1), show pedestal emissions at radii ≲3500AU that are not predicted. All lines except SO show a secondary peak within the approaching outflow cone. A dip or null in the visibilities caused by a sharp decrease in abundance with increasing radius is not observed in CS and only tentatively in SO.The emission of protostellar X-rays is supported by the good fit of the modeled SO and CS amplitude visibilities including an extended main peak in CS. The broad pedestals can be interpreted by far-UV irradiation in a spherically non-symmetric geometry, possibly comprising outflow walls on scales of 3500-7000AU. The extended CS and SO main peaks suggest sulfur evaporation near the 100K temperature radius. The effects of the corresponding abundance jumps may be reduced in visibility plots by smoothing due to inhomogeneity at the evaporation radius, varying by ±10% or more in different directions.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - stars: formation - submillimeter - astrochemistry - ISM: molecules - X-rays: ISM

VizieR on-line data: <Available at CDS (J/A+A/475/549): table1.dat fits/*>

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 3C 279 Bla 12 56 11.16657958 -05 47 21.5251510   18.01 17.75 15.87   ~ 2950 2
2 QSO J2015+371 BLL 20 15 28.72978661 +37 10 59.5147372     21.82 21.4   ~ 275 2
3 RAFGL 2591 Y*O 20 29 24.8230 +40 11 19.590           ~ 610 0
4 NAME BL Lac BLL 22 02 43.2913536816 +42 16 39.979416792   15.66 14.72     ~ 2192 1

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